09.10 – Summary: Our Eyes in the Sky

What is a black hole? Do they really exist? How do they form? How are they related
to stars? What would happen if you fell into one? How do you see a black hole if they
emit no light? What’s the difference between a black hole and a really dark star?
Could a particle accelerator create a black hole? Can a black hole also be a worm
hole or a time machine?
In Astro 101: Black Holes, you will explore the concepts behind black holes. Using the theme of black holes, you will learn the basic ideas of astronomy, relativity, and quantum physics.
After completing this course, you will be able to:
• Describe the essential properties of black holes.
• Explain recent black hole research using plain language and appropriate analogies.
• Compare black holes in popular culture to modern physics to distinguish science fact from science fiction.
• Describe the application of fundamental physical concepts including gravity, special and general relativity, and quantum mechanics to reported scientific observations.
• Recognize different types of stars and distinguish which stars can potentially become black holes.
• Differentiate types of black holes and classify each type as observed or theoretical.
• Characterize formation theories associated with each type of black hole.
• Identify different ways of detecting black holes, and appropriate technologies associated with each detection method.
• Summarize the puzzles facing black hole researchers in modern science.

教學方

Sharon Morsink

Associate Professor

腳本

[MUSIC] Black holes don't emit light, but that doesn't mean that we can't detect them. Just one of the ways is through their interactions with background light, gravitational lensing. When a black hole is in a binary system, the companion star can be seen. In some cases, mass flows from the companion star into an accretion disk surrounding the black hole, which then emits light. The electromagnetic radiation emitted by the disk, jet and corona varies in time as the rate of in-falling gas changes. Super massive black holes, in the centers of galaxies, also give away their presence through the energy released by accretion. Jets of gas, energized by gravitational potential energy, interact with the black hole's host galaxy, affecting the formation of nearby stars in the galaxy. Supermassive black hole jets are thought to accelerate particles such as protons and neutrinos. Perhaps this is the origin of cosmic rays. Isolated black holes most certainly exist in our galaxy but are hard to detect. They can give away their location when they travel between a distant star and the Earth. The gravitational micro-lensing effect briefly causes the light from the distant star to appear brighter. Scientists have learnt all these things through the observation of light or electromagnetic radiation, but this isn't the only tool they have at their disposal. Recent projects like LIGO and Virgo are built to be incredibly sensitive gravitational wave observatories. What are they looking for? They're looking for evidence of merging black holes which generate gravitational radiation. That's right, waves in the fabric of space-time.